The present invention is directed to an improved reflector structure that is substantially more impact resistant than prior reflector structures. In particular, a lens member having a plurality of reflector elements is provided with continuous peripheral walls surrounding each individual reflector element to form a cell. In cube-corner type reflector structures of the type contemplated by the present invention, the reflector elements provide night reflectivity, but contribute little to daylight visibility of the reflector; the underlying support surface and the peripheral walls of the reflector structure are intended to provide daylight visibility.
Generally, reflector structures are made for exposure to all types of weather conditions and abuse incident to such use. They are subject to vandalism and impacts from stones, birds and other objects and debris. One form of the novel reflector structure of the present invention, when used as a pavement marker is specifically designed to receive heavy loads and to resist the high impact forces exerted by vehicle tires impinging thereon. Use of the present invention also eliminates the expensive steps of metallizing the reflector elements and "potting" the marker, with the attendant drop in reflective efficiency.
U.S. Pat. No. 4,208,090, assigned to applicant's assignee, discloses a reflector structure including a body of transparent material having a front face and a rear face. The rear face includes a plurality of cells, each surrounded by a support wall and each illustrated cell containing at lease four cube-corner type reflector elements therein. A problem with pavement markers made in accordance with the '090 patent is that the cells, having multiple reflector elements therein, experience beam type loading, and thus the impact of vehicle tires and of stones, pebbles and the like lodged in the tire thread tend to fracture the cells at relative low impact values. Fractures then allow the cells to fill with dirt and moisture, causing a loss of optical efficiency in all the reflector elemnts of the cell. Placing fewer than four reflector elements in each cell disclosed in the '090 patent and using the support wall structure disclosed therein, would significantly decrease the night time visibility of such a marker because proportionally less area would be used for reflector elements. By contrast, the present invention allows proportionally greater area for reflector elements while preventing impact fractures with an improved support structure.
U.S. Pat. No. 4,227,772, also assigned to applicant's assignee, discloses a pavement marker which includes a base having at least one support wall positioned in use in the direction of an oncoming vehicle. The support wall contains a number of recesses. A lens member places a plurality of retrodirective cube-corner type reflector elements into each recess and hermetically seals the reflector elements in the recesses to form a cell. The relatively low impact resistance of the cells, again caused by beam type loading and the notch effect of the plastic molding, results in fractures at lower impact values than achieved in epoxy filled type pavement markers, such as the type made under Heenan U.S. Pat. No. 3,332,327, assigned to applicant's assignee.
Other attempts to provide adequate strength to withstand impact forces in cell type reflectors have included filling the air cells with epoxy resin or the like. For instance, U.S. Pat. No. 3,924,929, granted to Holmen et al., in FIG. 3 discloses particulate matter being used, in part, to strengthen the construction of the reflector. However, while filling the cell with various materials may increase durability, it also may cause a loss of optical efficiency as high as fifty percent, as well as increase the number of manufacturing steps, material costs and resultant cost of the reflector.
U.S. Pat. No. 2,351,080, granted to Swarovski, discloses a mass of material into which reflective elements are individually embedded. The elements, presumably glass, are provided with facets overlapped by the embedding mass at the border of the light reflecting faces. Although the embedding principle theoretically increases the impact resistance of the reflector, the principle does not achieve the result of the present invention, with attendant savings in cost and efficiency. Moreover, the reflective elements of an air cell reflector would be rendered non-reflective, if the embedding mass were in contact with the faces, as disclosed in Swarovski.